The proton exchange membrane fuel cell (PEMFC), also referred to as the polymer membrane fuel cell, comprises at least a fuel cell, as shown in FIG. 1. The fuel cell 10 comprises a membrane electrode assembly (MEA) 110, two gas diffusion layers (GDL) 105 and 107, and two fluid flow plates 101 and 102. The gas diffusion layers 105 and 107 are clipped between the fluid flow plates 101 and 102. The membrane electrode assembly 110 is clipped between the gas diffusion layer 105 and 107. The fluid flow plates 101 and 102 are provided with respective flow channels 103 and 104 for delivering and distributing reactant fluids required by the fuel cell and the residual fluid after reaction. The delivered and distributed fluid includes hydrogen or humid hydrogen on the anode side and the residual fluid and water as a product after reaction on the cathode side.
The membrane electrode assembly 110 experiences oxidation on the anode side and reduction on the cathode side. When hydrogen on the anode side contacts the catalyst 106 (or 108, generally formed of platinum or platinum-based alloys) adjacent to the proton exchange membrane 109, hydrogen molecules are dissociated into hydrogen ions and electrons. The electrons move from the anode to the cathode by way of a bridge connecting the anode and the cathode and a load connected to the bridge, while the hydrogen ions move from the anode to the cathode directly through the proton exchange membrane 109. It is noted that the proton exchange membrane 109 is a membrane with humidity and only allows hydrogen ions accompanied by water molecules to pass through while. On the cathode side, with the catalyst 108 (or 106), the electrons by way of the bridge are combined with oxygen to produce oxygen ions, which are immediately combined with the hydrogen ions passing through the proton exchange membrane 109 to produce water molecules. Thus, electrochemical oxidation-reduction reaction is completed.
By using such electrochemical reaction, the proton exchange membrane fuel cell (PEMFC) exhibits high power generation efficiency, environment-friendliness, rapid response and capability in forming cell stacks to increase the voltage of the cell and/or the current due to enlarged electrode area, as shown in the top view in FIG. 2. As the fuel cell is supplied with continuous reactant fluid, it provides the load with continuous power. Accordingly, the proton exchange membrane fuel cell can be used as a power source for small systems and can be designed in a large power plant, distributed systems and mobile systems.
In FIG. 2, the fuel cell stack 20 comprises stacked fuel cells 10 and two end plates 201 and 202, two current collectors 205 and 206, and a plurality of fasteners 203 and 204.
The fluid flow plates can be structured as they are designed. Generally, the fluid flow plates on the anode side and on the cathode are similar or identical. FIG. 3 is a cross-sectional view of FIG. 2 and shows a fluid flow plate. The fluid flow plate 30 has one face being a fluid flow face 305 for receiving a reactant fluid, and a non-active surface 308. The fluid flow plate 30 is provided with an inlet manifold 301 for receiving a fluid 210 from a source and at least an outlet manifold 302 for exhausting a reacted fluid 211 to be exhausted. The fluid flow face 305 is provided with at least one flow channel 306 for distributing and delivering the fluid. The flow channel 306 comprises an entry 304, an export 307, and at least a groove inserted with a sealing member 303 for sealing the fuel cell to complete a fluid flow plate.
For a fuel cell stack, after passing through the inlet manifold 301, the reactant fluid 210 flows into each flow channel 306 for electrochemical reaction in the fluid flow plate 30 of a fuel cell 10, while the reacted fluid 211 is exhausted from the outlet manifold 302. Such mechanism is a key to the reliability and stability of the fuel cell. Moreover, gas-tightness is another key to the functionality of the fuel cell. If the fuel cell is not gas-tight, leakage or crossover of the reactant fluid occurs on the cathode side and the anode side, which causes damages to the fuel cell stack. At the entry 304 and the export 307 of the flow channel 306, the fuel cell is weakly supported and gas-tightness is likely to fail. As the assembly stress is distributed over each components of the cell stack 20 and the portion where the inlet manifold 301 and the outlet manifold 302 are disposed is not supported, the membrane electrode assembly 110 and the gas diffusion layers 105 and 107 may come apart easily to cause crossover of reactant fluid, or the membrane electrode assembly 110 and gas diffusion layer 105 and 107 may sink at the entry 304 and the export 307 of the flow channel 306 to block the fluid flowing into or out of the fluid flow plate 30. Therefore, it has become an important issue of how to let the fluid flow into or out of the fuel cell without obstruction while maintaining the gas-tightness of the fuel cell.
U.S. Pat. No. 6,017,648 discloses an insertable fluid flow passage bridge piece and a method for manufacturing the same. The bridge piece is inserted into an open-face fluid flow channel of a fluid flow plate. The bridge piece is provided with at least one flow channel on one face so that the fluid is allowed to flow through. Moreover, the method for manufacturing the bridge piece is disclosed.
U.S. Pat. No. 6,410,179 discloses a fluid flow plate having a bridge piece. The bridge piece is disposed on an open-face fluid flow channel of a fuel cell fluid flow plate. The bridge piece has a face for defining a groove adapted to receive a sealing member and the other face for defining a flow channel, through which the fluid is allowed to flow.
The above mentioned patents use a bridge piece, which causes difficulty in aligning components and dislocations of components during assembly and results in troubles in mass production.
U.S. Pat. No. 6,500,580 discloses a fuel cell fluid flow plate for promoting fluid service, wherein an inlet channel is connected to a manifold for distributing a reactant in the fuel cell and dive through hole is defined in and extends through the fluid flow plate so that the dive through hole and the inlet channel facilitate transmission of a portion of the fluid to the flow channel.
U.S. Pat. No. 6,607,858 discloses an electrochemical fuel cell stack with improved reactant manifolding and sealing, wherein separator plates are provided with ports comprising walls that have faces that are angled more than 0 degree and less than 90 degrees with respect to the direction of fluid flow.
In the above mentioned patents, though holes are required and thus drilling and alignment processes are performed. Moreover, it is also required that the fluid flow face and the low channels on both sides of the non-active surface are aligned so that the fluid can flow without obstruction.